Bushing insulator



Jan. 15, 1935. A. 0. AUSTIN 1,983,151

BUSHING INSULATOR Filed Dec. 5, 1931 2 Sheets-Shet 1 NVENTOR Arf/u/r 0.41/4/07 ATTORNEY Jan. 15, 1935. v ug-rm 7 1,988,151

BUSHING INSULATOR Filed D60. 3, 1931 I 2 Sheets-Sheet 2 Arf/zur 0.Awf/n.

BY W4 4% ATTORNEY Patented Jan. 15, 1935 BUSHING INSULATOB Arthur 0.Austin, near Barber-ton, Ohio, assignor,

by mesne assignments, to The Ohio Brass Company, Mansfield, Ohio, acorporation of New Jersey Application December a, 1931, Serial No. 51amClaims. (01. 173-318) This invention relates to bushing insulators andhas for one of its objects the provision of an insulator of the classnamed which will have maximum efllciency for the size of the opening 5through which the bushing extends.

Another object is to provide a bushing insulator which will be simpleand economical to manufacture and easy to install.

A further object is to provide an insulator which will not permit oil orother insulating liquid to leak through the insulator Joints.

A further object is to provide a bushing insulator which shall be ofimproved construction and operation.

Other objects and advantages will appear from the following description.

The invention is exemplified by the combination and arrangement of partsshown in the accompanying drawings and described in the followingspecification, and it is more particularly pointed out in the appendedclaims.

In the drawings:

Fig. 1 is an elevation with parts in section showing one embodiment ofthe present invention.

Figs. 2, 3, and 4 are views similar to Fig. 1 showing other forms of theinvention.

In high voltage bushings, particularly those used for transformers,circuit breakers and other equipment with line voltages below 100 K. V.,it is frequently very diiflcult to obtain a bushing of small size whichhas the necessary dielectric strength and flashover voltage and iseconomical in cost. In many bushings, also, it is diflicult to maintaina tight joint between the bushing and the flange for attaching thebushing to the case so that the joint-will not leak oil, particularlywhei-e changes in temperature are very material and the current is sohigh that it is necessary to use flanges of non-magnetic material.

In many installations already operation, it

becomes desirable to replace bushings with others the bushing consistsessentially of an outer insulating member 10, an inner insulating member11-, aflange 12, a conductor 13, and a compressing system comprisingupper and lower plates 14- and 15 respectively, and springs 16 actingthrough the conductor 13 to hold the insulating members 10 and 11 andthe flange 12 together. An expansion chamber 17 may be added and thenecessary terminals to provide a conducting cable drawn through thebushing or for utilizing the conduction of the tubular member 13. Theinsulating member 11 furnishes the outside or insulating sleeve on thelower end of the bushing and is cemented to the flange 12 and telescopesinto the upper insulating shell 10. This arrangement provides aninsulating baflle for the upper portion of the bushing of the diameterof the sleeve 11 at the point of maximum stress where it is joined tothe flange 12 and where it passes through the opening 18 of the case ofthe transformer or circuit breaker.

Since the clamping means exerts a longitudinal pressure on the member 11through the flange 15 and gasket 19, this pressure in turn may betransmitted through the cement joint 20 to the flange 12. This exertspressure on the gaskets 21 and 22, insuring a tight joint at all timesat the gaskets 19, 21 and 22. Since the pressure on these gaskets ismaintained by the resiliency in the compression springs 16, tightnesswill be maintained even though the center conductor expands or contractsor the gaskets change in volume due to pressure. Bolts 23 may be used tohold the springs 16 under compression while the bushing is beinginstalled, after which the force of the springs is taken by the plateli'and nut 24. The bolts 23 may then be removed or left to hold theplate 14 from rotation on its axis; the nut 24 being screwed down toposition to take the force of the springs 18.

The flange 12 is secured to the transformer or circuit breaker case 25by clamping the face 26 of the flange 12 against gaskets 27 and 30placed betweenthe lower face 26of the flange 12 and the shoulder 28surrounding the opening through the top wall of the transformer orcircuit breaker case 25. The clamping is done by bolts or cap screws 29.With this construction, any leakage through the joint 20 between thebody of the flange 12 and the member 11 will not reach the outside ofthe bushing, which is one of the most serious objectionsto manybushings.

Where a conservator tank is used in connection with the housing 25 inwhich the surface of. the oil is above that in the bushing or where adrop of the surface level of the oil in the bushing would be likely tohave any eifect upon the operation, it is desirable to prevent leakagebetween the interior of the bushing and the interior of the tank throughthe joint 20. F 'or this i a and will expand against the insulatingmember 11, thereby insuring a tight joint due to the clamping pressure.

A similar joint may be provided at the upper end of the flange 12 ifdesired by using a metal ring 32 bearing on the gasket 21 on top of theflange 12. The pressure between themetal piece 32 and the gasket 21 willforce the gasket 21 inward and tend to create a tight joint. The metallayer 32 above the gasket will prevent leakage through the gasket andalso extend the pressure area inwardly from the bearing surface oi themember 10. The ring 32 may have an upwardly extending flange 33 actingas a flux control or screen.

In some cases, as shown in Fig. 2, it is possible to bring the bearingsurface of the outer dielectric member 35 very close to the inner member36 so that an additional metal ring is not needed for creating pressure.The bearing surfaces adjacent to the gasket may be beveled, as shown at37, so as to force the gasket 38 against the member 36, thereby sealingthe joint.

It will be seen that the construction is such that a tight housingorshell may be provided so that the insulator parts may be covered withoil or compound so that there will be no tendency to discharge over theupper end of the sleeves or bafllesll and 34 in Fig. 1, and 36 in Fig.2. 'The construction insures tightness at all times between the outerporcelain shell and the flange used for attaching the bushing, hence, ifa tight joint is provided between this flange and the transformer orcircuit breaker case, leakage to the outside is prevented. This isparticularly important for equipment having oil reservoirs orconservator tanks for raising the oil level above the flange.

Since the upper portion of the bushing may be given a large diameterwithout interfering with a small bolt circle, it is evident that adistinct electrical advantage is gained as the upper end of this bushingmay be provided with the same field conditions as that of oil fllledbushings. A large. diameter to reduce the stress may be used without thenecessity of making thick parts. The construction also permits ofinternal shielding so as to cut down the surface stress.

With the construction used, the entire length of the upper member isutilized for insulation, thereby making it possible .to reduce thelength and cost of the bushing for given voltage requirements. The smalldiameter of the flange 12 makes it possible to use a bolt circle smallerin diameter than the lower end of the upper insu-' lating shell 10 or35. This is particularly important where the diameter of.the bushing islimited, owing to the opening in transformer or circuit breaker case.Since a tight construction is insured, the insulating baflles projectinginto the upper cone may be covered with oil or compound which willprevent fiashover inside the case or upper shell 10.

The construction has the advantage that the insulating member subjectedto most severe dielectric stress may be made of approximately thediameter of the opening in the transformer or circuit breaker case. Thisinsures an insulating member of fairly uniform section and of maximumdielectric strength and reliability and one which may be made by simplyextruding the clay or by other convenient methods.

While the diameter of the upper end of the inner member 11 or 36 may besomewhat larger than that where it passes through the opening in thetransformer or circuit breaker case or where it is attached to the metalflange, it need not be large enough to form the weather sheds, as theseare formed on the upper shell 10 or 35. This is a distinct advantage asa tubular member which must have a small opening and have a largediameter so as to form the weather sheds is difficult and costly toform, and the dielectric reliability is inferior to a piece formedpractically to size. With the construction shown, a large diameter maybe obtained at the upper end without restriction as to the use of asmall hole in the inner piece. In addition, the electrical stress on theupper shell is largely in a longitudinal direction under normaloperating conditions.

In Fig. 2 a single dielectric tube 36 extends through the opening in thehousing 25, the opening through the tube being of a proper size toreceive the conductor rod 39 while the tube is cemented directly in theflange 12. The flange 12 is secured to the housing-25 by cap screws 29,as in Fig. 1, the screws 29 being threaded into a ring 40 which engagesthe outwardly extending shoulder 28 surrounding the opening in thecovershoulder 28 formed outwardly over the ring after the ring is inplace. The outer member 35 is clamped upon the gasket 38 by theconductor rod 39 and spring 41 in a manner similar to the constructionshown in Fig. 1 except that in Fig. 2 a single spring 41 is used inplace of the plurality of springs 16, shown in Fig. 1.

Fig. 3 shows a construction somewhat similar to Fig. 2 but in thisfigure a packing gland is shown at 42 in which the packing is.compressed by a beveled face 43 of the gland member 44. An additionalgasket 45 may be inserted between the lower face of the member 44 andthe upper face of the shoulder 28 on the housing member 25. The innerdielectric member 46 may be provided with a flange 4'! forming a recess48, the inner surface of which is metallized in any suitable way toprovide an electrostatic flux control. The outer dielectric member 49rests upon the flange 50 and is provided with a gasket 51 to form atight joint. The flange 50 may be provided with a filling opening 52closed by a plug 53. The flange 50 is cemented to the inner dielectricmember 46 and the two dielectric members are held together by theconductor rod 54 provided with a spring 55 which compresses the gasket51 and also the gaskets 56 and 57 so that the inside of the bushing iscompletely closed and the joints at 51, 58 and,57 are held tight by thespring 55. The bolts 29 hold the bushlngin place on the housing 25 and,at the same time, compress the packing 42 and 45 to prevent leakagethrough the cement joint 58. A closed turn conductor 59 may beinterlinked with the spring 55 to prevent heat losses in the spring 55,as explained in my prior application Serial Number 565,047. Theconductor from the electrical apparatus in the housing is connected to aterminal member 102 having a spring socket for receiving the terminalmember 103 threaded on the end of the conductor tube 54. The terminal102 has a flexible cable 104 secured thereto which is drawn upwardlythrough the tube 54 when the bushing is installed to pull the terminal102 into place. The flexible draw cable 104 may be secured in place bylock nuts 105 at its upper end which rest on the upper end of the tube54.

In the modification shown in Fig. 4, the inner tubular dielectric memberis formed of two separate sleeves, the inner sleeve 60 having a shoulder61 upon which the lower end of the outer sleeve 62 bears. The sleeve 62is secured to the flange 63 by cement 64. A ring 65 is provided with aseat 66 upon which the lower end of the upper dielectric member 87rests; a gasket 68 being provided to insure a tight joint. The upperedge of the fiange 63 is beveled to provide a gland for receiving apacking 69 and the inner face of the flange 63 fits closely to the outerface the tubular member 62 so that the packing 69 may form a tight jointat this point. The flange 63 also fits closely against the outer surfaceof the dielectric sleeve 62 adjacent the lower end of the flange at '10,and a gasket '11 is placed between an offset portion of the fiange 63and the housing '12. A metalring 73 may be provided to bear against thegasket '11 and a thin gasket '14 may be placed between the ring '13 andthe housing '12 or this surface may be covered with a coat of paint,varnish or other material which will prevent leakage at this point.

I claim:

1. The combination with a housing having an opening through the upperwall thereoi, a' conductor extending through said opening, a tubulardielectric member surrounding said conductor and fitting closely withinsaid opening, a flange cemented to the outer suriace of said tubulardielectric member and bolted -to said wall, said flange having anupwardly extending portion provided with a beveled upper edge forming agland, packing for said gland, a ring surrounding said tubulardielectric member and bearing upon said packing, an outer tubulardielectric member telescoping with the upper end of said first-namedtubular dielectric member and having its lower end bearing upon saidring, and resilient means for connecting said outer tubular dielectricmember with said conductor for exerting yielding pressure on said ringto compress the packing in said gland and to hold said outer tubulardielectric member in position.

2. The combinaticn with a cover plate having an opening therethrough, ofa conductor extending through said opening, a dielectric sleevesurrounding said conductor, a metallic fitting cemented to the outerperiphery of said sleeve, a gasket bridging the cement joint betweensaid sleeve and fitting and bearing upon said cover plate, threadedmembers for holding said fitting to said cover plate and for compressingsaid gasket to form a tight joint between said sleeve and cover plate,said fitting having a radially projecting shoulder thereon, a dielectricshell disposed over one end 01' said sleeve and having its open endbearing upon said shoulder, holding members attached to said conductorand bearing against the sleeve and shell respectively, and resilientmeans cooperating with said conductor and said holding members forpressing said shell against said shoulder to form a tight joint.

3. The combination with a wall plate having an opening therethrough, ofa conductor extending through said opening, a dielectric sleevesurrounding said conductor, a metallic band surrounding said sleeve andcemented thereto and having a radially extending flange thereon, agasket disposed between said flange and said wall plate and bridging thejoint between said sleeve and band, threaded members for securing saidflange to said wall plate and for compressing said gasket, packingengaging the edge of said band opposite said flange and bearing againstthe face of said sleeve, a metallic ring having a shoulder engaging saidpacking and having a radially extending flange, a dielectric shelldisposed over the endof said sleeve and bearing upon the last namedflange, holding members secured to said conductor and engaging saidsleeve and shell respectively, and a spring cooperating with saidconductor and said holding members for pressing said shell against saidlast named flange.

4. An insulator comprising a dielectric member, a metal fitting for saiddielectric member, cement connecting said dielectric member and fitting,said dielectric member having a shoulder thereon adjacent the jointformed by said cement, a gasket engaging said metal fitting and saidshoulder and bridging the joint formed by said cement and overlappingsaid metal fitting and shoulder at each side of said joint, and meansalso overlapping said metal fitting and shoulder.

and engaging the side of said gasket opposite said fitting and shoulderfor compressing said gasket to press the same against said fitting andshoulder to prevent leakage through the joint formed by said cement.

5. A bushing insulator comprising a dielectric member, a flange cementedto the outer surface of said dielectric member, a shoulder on saiddielectric member registering with one iace of said flange, a gasketbridging the joint between said flange and said dielectric member andoverlapping said shoulder and the registering face of said flange, andmeans also overlapping said shoulder and flange and engaging the side ofsaid gasket opposite said shoulder and flange and pressing said gasketin the direction of the axis of said bushing insulator to hold saidgasket against said shoulder and said flange.

ARTHUR o. AUSTIN.

